A senior federal law enforcement official tells us the government is tracking the phone numbers we call in an effort to root out confidential sources.

"We" means "reporters."

"It's time for you to get some new cell phones, quick," the source told us in an in-person conversation.

We do not know how the government determined who we are calling, or whether our phone records were provided to the government as part of the recently-disclosed NSA collection of domestic phone calls.

Other sources have told us that phone calls and contacts by reporters for ABC News, along with the New York Times and the Washington Post, are being examined as part of a widespread CIA leak investigation.

One former official was asked to sign a document stating he was not a confidential source for New York Times reporter James Risen.

Our reports on the CIA's secret prisons in Romania and Poland were known to have upset CIA officials.

People questioned by the FBI about leaks of intelligence information say the CIA was also disturbed by ABC News reports that revealed the use of CIA predator missiles inside Pakistan.

Under Bush Administration guidelines, it is not considered illegal for the government to keep track of numbers dialed by phone customers.

The official who warned ABC News said there was no indication our phones were being tapped so the content of the conversation could be recorded.A pattern of phone calls from a reporter, however, could provide valuable clues for leak investigators.